Featured Research

from universities, journals, and other organizations

Geometry affects drift and diffusion across entropic barriers

Date:

June 29, 2010

Source:

American Institute of Physics

Summary:

Understanding particle diffusion in the presence of constrictions is essential in fields as diverse as drug delivery, cellular biology, nanotechnology, materials engineering, and spread of pollutants in the soil. When a driving force is applied, displacement of particles occurs as well as diffusion. A new paper quantifies the effects of periodic constrictions on drift and diffusion in systems experiencing a driving force.

Share This

An understanding of particle diffusion in the presence of constrictions is essential in fields as diverse as drug delivery, cellular biology, nanotechnology, materials engineering, and spread of pollutants in the soil. When a driving force is applied, displacement of particles occurs as well as diffusion.

Related Articles

A paper in the Journal of Chemical Physics, which is published by the American Institute of Physics (AIP), quantifies the effects of periodic constrictions on drift and diffusion in systems experiencing a driving force.

In a uniform cylinder, both the mobility and the diffusion coefficient of the particle are independent of the driving force. This is not true, however, when the cylinder diameter varies. Constrictions provide periodic entropic barriers, which slow down drift and diffusion when the driving force is weak.

This research examined two types of cylinders. In the first, a tube consisted of sequential spherical compartments connected by small circular openings. The driving force suppressed the slowdown due to the constrictions. The particle subjected to a strong driving force showed no change in effective diffusion coefficient or mobility as a result of the periodic restrictions. In a tube of cylindrical chambers, however, the results were dramatically different. Under a strong driving force, mobility decreased while the diffusion coefficient became extremely large due to intermittency that occurred in the particle transitions between openings connecting neighboring compartments.

While author Alexander Berezhkovskii of the National Institutes of Health acknowledges that the original idea for the project was inspired by devices that deliver drugs locally in small amounts, he looks at the research as a quest for a broader understanding. "Nature is very complicated because of geometry, but we are looking for something simple that underlies the complexity," he says.

More From ScienceDaily

More Matter & Energy News

Featured Research

Mar. 3, 2015 — By examining the forces that the segments of mosquito legs generate against a water surface, researchers have unraveled the mechanical logic that allows the mosquitoes to walk on water, which may ... full story

Mar. 3, 2015 — Researchers have developed a new way of rapidly screening yeasts that could help produce more sustainable biofuels. The new technique could also be a boon in the search for new ways of deriving ... full story

Mar. 3, 2015 — Major cities in the UK are falling behind their international counterparts in terms of their use of smart technologies, according to a new study. The research has found that smart cities in the UK, ... full story

Mar. 3, 2015 — Scientists have explored friction at the microscopic level. They discovered that the force generating friction is much stronger than previously thought. The discovery is an important step toward ... full story

Mar. 3, 2015 — Micro-drones are already being put to use in a large number of areas: These small aircraft face extensive requirements when performing aerial observation tasks or when deployed in the field of ... full story

Mar. 3, 2015 — Recent research contributes to the effort to determine the nature of dark matter, one of the most important mysteries in physics. As indirect evidence provided by its gravitational effects, dark ... full story

Mar. 3, 2015 — Physicists have shown for the first time that electrons in graphene can be moved along a predefined path. This movement occurs entirely without loss and could provide a basis for numerous ... full story

Featured Videos

Forensic Holodeck Creates 3D Crime Scenes

Reuters - Innovations Video Online (Mar. 3, 2015) — A holodeck is no longer the preserve of TV sci-fi classic Star Trek, thanks to researchers from the Institute of Forensic Medicine Zurich, who have created what they say is the first system in the world to visualise the 3D data of forensic scans. Jim Drury saw it in operation.
Video provided by Reuters

Solar Plane Passes New Test Ahead of World Tour

AFP (Mar. 2, 2015) — A solar-powered plane made a third successful test flight in the United Arab Emirates on Monday ahead of a planned round-the-world tour to promote alternative energy. Duration: 01:05
Video provided by AFP

Electric Hydrofoiling Watercraft Delivers Eco-Friendly Thrills

Reuters - Innovations Video Online (Mar. 2, 2015) — The Quadrofoil is a high-tech electric personal watercraft that its makers call a &apos;sports car for the water&apos;. When it hits 10 km/h, the Slovenian-engineered Quadrofoil is lifted above the water onto four wing-like hydrofoils where it &apos;flies&apos; above the surface with minimal water resistance. Matthew Stock reports.
Video provided by Reuters

Related Stories

May 15, 2014 — Researchers optically trapped a cloud of gas a billion times colder than air in a very low-pressure vacuum, and found a lower speed limit to diffusion. Assembling the puzzles of quantum materials is, ... full story

July 15, 2013 — The Internet, motorways and other transport systems, and many social and biological systems are composed of nodes connected by edges. They can therefore be represented as networks. Scientists ... full story

Dec. 21, 2012 — A new models suggest devising means of probing a surface at a sub-micrometric level as this will help us understand how electrons' diffusion affects long-range attractive forces. Theoretical ... full story

Dec. 20, 2012 — Waves do not spread in a disordered medium if there is less than one wavelength between two defects. Physicists have now proved Nobel Prize winner Philip W. Anderson's theory directly for the ... full story

Sep. 26, 2012 — A recent study characterizes the movement of rhodopsin, a GPCR and member of a large family of transmembrane receptors responsible for many cellular responses and involved in many human ... full story

ScienceDaily features breaking news and videos about the latest discoveries in health, technology, the environment, and more -- from major news services and leading universities, scientific journals, and research organizations.